一个单核Fe(III) 单分子磁铁,具有3/25/2旋转交叉旋转
Susanne Mossin1, Ba L Tran, Debashis Adhikari
1Center for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, 2800 Lyngby, Denmark. slmo@kemi.dtu.dk
Journal of the American Chemical Society
|July 24, 2012
概括
这项研究揭示了一个铁复合体,它从80K以上的S = 3/2到S = 5/2呈现出意想不到的旋转转变.这种行为表明它作为具有定义能量屏障的单个分子磁铁而起作用.
科学领域:
- 无机化学 无机化学
- 材料科学 材料科学 材料科学
- 磁电化学 磁电化学 磁电化学
背景情况:
- 新型铁复合物的合成和表征对于开发先进的磁性材料至关重要.
- 了解过渡金属复合体中的旋转转换是设计具有可调节性质的分子磁铁的关键.
研究的目的:
- 为了研究空气稳定的铁复合物的磁性和旋转状态过渡[(PNP) FeCl(2) ] (1).
- 阐明控制观察到的旋转交叉行为的结构和电子因素.
主要方法:
- 使用直流和交流SQUID磁力测量的磁性敏感度测量.
- 可变温度的Mössbauer光谱和X波段电子磁共振 (EPR) 光谱.
- 多边的X射线吸收光谱 (XAS) 和可变温度的单晶X射线衍射.
主要成果:
- 综合体1显示出一个意想不到的旋转转变,从S = 3/2到S = 5/2在80K以上.
- AC SQUID数据证实了单个分子磁铁的行为与热激活屏障 (U(eff) = 32-36 cm(-1)).
- 结构和光谱数据将旋转转变与铁的协调几何和电子结构的变化相关联.
结论:
- 铁复合物[PNP) FeCl (2) ]表现出温度诱导的自旋交叉,作为单个分子磁铁起作用.
- 观察到的旋转过渡归因于四重奏和六重奏电子状态的接近,受联体相互作用和几何学的影响.
- 这项工作为基于铁复合物的分子磁性材料的设计原则提供了洞察力.
相关概念视频
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:31Ferromagnetism
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
01:26Diamagnetism
Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
01:17Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...